High strength crystalline oriented filaments

ABSTRACT

THIS INVENTION RELATES TO POLYAMIDE FILAMENTS HAVING A NEW CRYSTAL STRUCTURE, WHEREBY YARNS OF HIGH TENACITY AND HIGH THERMAL STABILITY ARE PRODUCED.

United States Patent O M US. Cl. 260-78 Claims ABSTRACT OF THE DISCLOSURE- This invention relates to polyamide filaments having a new crystal structure, whereby yarns of high tenacity and high thermal stability are produced.

This application is a continuation-in-part of my application Ser. No. 693,725, filed Dec. 27, 1967 and now abandoned.

DETAILED DESCRIPTION OF THE INVENTION Polyamides from bis(4 aminocyclohexyl) methane (herein abbreviated PACM) and various aliphatic diacids are known, for example from US. Pat. Nos. 2,512,606; 3,249,591; 3,361,859; and 3,393,210.

It has now been found that filaments spun from polyamides formed from PACM and aliphatic diacids of 12, 14 and 16 carbon atoms can be prepared in such a way that they have a specific crystal structure; yarns with this crystal structure are highly desirable for all end uses, particularly tire cords, requiring high strength, high modulus and low shrinkage. In addition, for maximum melting point and shrinkage stability such polymers are preferred over PACM-11, PACM-13 and PACM-15.

This invention provides a high-molecular-weight, highmelting, crystalline, oriented filament of the polymer of his (4aminocyclohexyl)methane of 70 to 100% transtrans stereo-isomer content and an aliphatic diacid of 12, 14 or 16 carbon atoms, the said filament having a transverse crystal spacing or d value of 4.3 to 4.7 A., as determined from the strongest equatorial reflections in a Bragg X-ray diffraction pattern, and a c axis spacing of at least 23, 25 or 27 A., respectively. As explained herein after, the crystals have chains which are at least 86% fully extended. The preferred filaments exhibit a tenacity in excess of six grams per denier.

FILAMENT CRYSTAL STRUCTURE The structure and processing of the filaments of this invention prepared from PACM and diacids of 12, 14 or 16 carbon atoms are described in detail below with respect to filaments of PACM-dodecanedioic acid (PACM12), which is especially preferred. When filaments of the reaction product of P-ACM and aliphatic dicarboxylic acids of 12, 14 or 16 carbon ators are drawn to moderate draw ratios, they show an X-ray diflraction pattern characterized by a single diffuse halo on the equator (perpendicular to the fiber axis), indicating a notable lack of lateral order. The radius of this halo can be obtained by measuring the position of its peak intensity which might suggest a Bragg d spacing of about 4.7 A. However, as discussed on pages 631-3 of 'Klug and Alexander, infra, this is an incorrect interpretation of the diagram. This halo indicates that there is a frequently occurring interatomic distance of about 5.7 A. There is a single very sharp meridional reflection, indicating longitudinal order. For PACM- 12, this reflection corresponds to an apparent repeat unit length or c axis spacing of about 11.7 A. These yarns are essentially non-crystalline in the sense that they do not 3,655,630 Patented Apr. 11, 1972 exhibit three dimensional order. For convenience, they are called the LO form herein. When these filaments are annealed at constant length or while free to retract, they become highly crystalline and show an X-ray pattern with very strong first and second and weak third order meridional reflection. The distinguishing characteristic of this crystal form is that its strongest equatorial reflections corresponds to a d value of about 5.1 to 5.2 A. This crystal form is termed the A crystal, for convenience.

:In contrast to the LO structure and the A crystal pattern described above, filaments prepared in accordance with the instant invention have an X-ray pattern with the strongest equatorial reflection indicating a Bragg at value within the range of 4.3-4.7 A., as well as other characteristic differences which show existence of a new and different polymorph, termed the HT form for convenience. Filaments of the invention having a higher tenacity have an X-ray diagram characterized by a meridional 1st and 3rd layer line Bragg deflection which is separated into two spots. The angular separation of these spots increases with greater fiber orientation in the more highly drawn filaments of higher tenacity and a value of at least 10 is preferred. The crystal structure characterized by these separated meridional spots in the X-ray diagram is typical of, but not essential to the high tension or HT crystal form. At even higher levels of orientation, the meridional spots merge and appear again as a streak, and a new crystal, known as the EC crystal is formed. This crytal has an almost completely extended chain, as explained below.

The best-known polyamides, polyhexamethylene adipamide, polyhexamethylene sebacamide and polycaprolactam (66, 610 and 6 nylon) have a crystal structure with a constant c axis spacing which is directly proportional to the carbons in the repeating structural unit in the polymer chain. lIn contrast to these and most other polyamides which have been characterized as to crystal structure, the c axis spacing of PACM-l2, -14 and -16 polyamides previously known is shorter than calculated from Stuart and 'Brieglet models. For example, the average increase in chain length for adidtion of two CH units to the acid is not the expected 2.54 A. but is 1.96 A., and it is concluded that the chains are not fully extended and parallel to the c axis direction.

The HT crystal form appears when the polymer chains in the crystal are extended to at least about 86% of their theoretical length. When extended to about 98% of their theoretical length, both HT and EC crystal forms are present; with increasing orientation, more of the crystals are in the EC form, up to a chain extension of about 99% of theoretical. Such filaments will have maximum tenacity and are, consequently, preferred.

When both HT and EC crystal forms are present, the chains of the HT crystal may not be as fully extended as when the HT form is present alone. Both crystal forms have chains which are at least 86% fully extended.

It is emphasized that careful and precise X-ray tech niques are required to distinguish the forms, although the procedure is conventional. The EC form shows, as noted above, a c axis repeat corresponding closely to the length of models which are fully extended, i.e., 26.5 A. versus a theoretical 26.8 A. for PACM-12. A distinction from the HT diffraction pattern is best observed at the third layer line. This layer line spacing for the EC form does not show the variability in c axis spacing noted above for the HT form. The EC form shows a very strong equatorial diffraction at 4.3 A.

PROCESSING STEPS TO OBTAIN HT AND EC CRYSTAL Like all fiber-forming polyamides, PACM-12, 14 and -l6 filaments are spun and drawn to produce an oriented yarn useful for textile purposes. Drawing is facilitated when heat is applied by use of a heated snubbing pin, a heated plate or the two in combination. A suitable arrangement is shown by Hume, in U.S. Pat. 2,533,013. At filament drawing temperatures up to about 180 C., the drawn filaments have substantially no lateral order, but crystallization may be induced by annealing at constant length and/ or by a hot relaxing treatment, producing the A crystal, as explained above. When attempts are made to increase the tenacity of the non-annealed filaments by using higher draw ratios, they become delustered and weakened by transverse crack formation and thus are unsuitable for industrial uses.

Yarn which has the crystal structure of this invention has better properties (e.g., tenacity, elongation) as compared to non-crystalline yarns prepared at the same draw ratio (see Example II). When non-crystalline yarns are annealed, producing the A crystal structure, there is usually a loss in tenacity. HT crystal yarn is not only superior to A crystal yarn at low draw ratios, it is also much more drawable so that much higher draw ratios can be used, whereby yarns of tenacity up to 9 or more grams per denier may be produced. When tenacity is plotted versus elongation for these two types of yarns drawn at different draw ratios, it is seen that the HT-EC crystal yarns lie on a different curve from the A crystal yarns, showing their higher level of drawability and toughness.

To prepare the fiber of this invention, the proper drawing temperature is essential. It has been found empirically that the fiber should attain a specified minimum filament temperature. This temperature will vary, depending on the diacid used in the polymer, and also on the transtrans isomer content of the PACM. The relationships are given in the table; S is the trans-trans (tt.) stereoisomer content of the PACM in percent. The values are typical at draw ratios of about 4X.

TABLE 1 Drawing temperature (which Polymer: should be exceeded) C. PACM-12 130+S PACM-14 100+S PACM-16 70+S For higher draw ratios (e.g., 6X), temperatures to 20 C. higher should be employed. Methods for obtaining the desired isomer content are disclosed by Arthur in U.S. Pat. 3,347,917.

As an upper limit, the drawing temperature should not be so high that the fiber is drawn without producing a directly proportionate orientation; that is, viscous flow drawing must be avoided, Viscous flow drawing occurs when the filament temperature is too close to the polymer softening point. This type of drawing is observed when a plot of fiber orientation, fiber tensile properties, or drawing tension versus drawing temperature departs markedly from a fairly linear relationship. As an example, PACM-12 of 90% tt. PACM will show viscous flow drawing above about 260 C.

The filaments must be drawn sutficiently to produce yarn with a break elongation less than 40%; generally, the yarns are drawn to break elongations less than 20 to 30%. It is preferred to carry out the drawing in two stages with the high temperature exposure in the second stage. The process described in U.S. 3,091,015 is suitable. Any convenient heating means may be employed, such as a heated pin, a pipe, hot plate, liquid bath, radiant heat or a jet of heated fluid, provided that the filaments attain the specified temperature while they are stretched beyond their elastic limit. This final, high-temperature elongation will ordinarily be part of a drawing process wherein the filaments attain an orientation equivalent to that obtained with at least a 3.5x draw ratio.

TESTS AND STANDARD PROCEDURES Calculations of lateral spacing (d spacing) and c axis dimension are performed in the usual manner, described by H. P. Klug and L. E. Alexander, X-ray Diffraction Procedures, John Wiley and Sons, Inc., New York, 1954, particularly at p. 88, 89; 333-5; 567-8. The c axis spacing or T as used by Klug et al. supra is the vertical dimension of the unit cell. A recording densitometer is usually employed in determining the position of the maxima in the diffraction pattern. A fiat film camera is employed, with at least a 5 cm. sample to film distance, 7.5 cm. preferred.

The angular separation of the meridional spots described above is the angle on the film subtended by the meridian and a line from the center of the undiffracted beam which passes through the center of the reflection.

When yarn moduls is referred to, initial modulus is intended.

Break tenacity (T when tabulated, is the tenacity based on the denier of the yarn at the break point; it provides a useful method for comparing the strength potential of yarns having different tenacities and elongations. It is calculated from the relation.

where T is the normal tenacity in gm./den., and E is the elongation of the yarn at break, in percent.

All yarn tests are carried out at RH and 75 F.

Polymer and yarn viscosities reported herein are relative viscosities (RV), as defined in U.S. Pat. 2,385,890. Unless otherwise specified, a mixture of 50% formic acid and 50% phenol is used; the solution contains 3.7 gm. polymer in 50.0 ml. of solvent.

Tenacity, modulus and elongation are determined using an Instror tensile tester operating at elongation per minute. The yarn is relaxed for 24 hours at F., 55 relative humidity before testing. The percent of the theoretical or fully extended chain length is determined from the following expression:

c axis spacing observed 0 axis spacing calculated from bond lengths and angles EXAMPLE I Polymer is prepared by heating a stirred mixture of 8.2555 kg. of bis(4-aminocyclohexyl)methane of 70% trans-trans stereoisomer contact, 9.0357 kg. dodecanedioc acid, and 17.2 kg. water in an autoclave. The temperature is raised to 135 C., held for 30 minutes, and then 12.5 kg. of distillate is removed at atmospheric pressure. To the autoclave are then added 47 gm. of 25% acetic acid solution (stabilizer) and 39.6 gm. of a 2% solution of manganous hypophospite catalyst. The autoclave is then heated to 285 C. at 300 p.s.i.g., and the pressure is reduced to atmospheric over a minute period while increasing the temperature to 300 C. The autoclave is kept at 300 C. for 90 minutes, after which the polymer is extruded, cooled and cut to flake.

The polymer has a relative viscosity (RV) of 115, as measured in 98% formic acid. The polymer is dried, melted in a screw melter, and spun to a 34 filament yarn at a temperature of 295 C. The yarn has an RV of 212. The yarn is drawn 3.56X over a 100 C. snubbing pin. 'It then travels in a helical wrap around a pipe with a temperature gradient of to C. (increasing in the direction of yarn travel) to a total draw of 4.0x. The yarn denier is 260. Yarn properties are given in Table 2. In an attempt to increase yarn tenacity, the total draw ratio is increased, step-wise, to 5.24X; the properties of these yarns are also tabulated.

TABLE 2 Draw Tenacity, Elongation,

Test ratio g.p.d. percent Tb, g.p.d.

tained (T *=7.l). At plate temperatures above about 215 C., attainable yarn tenacity falls 01f because of viscous flow drawing, and consequent low orientation ing. Processing conditions and yarn properties are given in Table 3.

In contrast, when the same feed yarn is drawn 4.0x over the 150 C. pin and plates heated to 210, 230 and 240 C., and then annealed at 240 C., yarn (5) is produced that is better with respect to tenacity and elongation then either yarn (1) or (2), although the same draw ratio is employed. This yarn has the HT crystal form.

The draw ratio series is continued, as shown in the table, until an 8 g.p.d. yarn is produced at a 5.2x draw ratio. Processing conditions and yarn properties are listed in the table.

TABLE 3 Test Number 1 2 3 4 5 6 7 Total draw ratio 4.0 4. 0 4. 4. 4.0 5.0 5. 2 Plate 1, C 160 160 160 210 210 210 Plate 2, C 170 170 170 230 230 230 Plate 3, 180 180 180 240 240 240 Anneal temp., C 230 240 240 240 Drawn birefringence 0. 0461 0. 0456 0.0495 Crystal form A None None HT HT/ E 0 HT/ E C d Spacing 5. 0 4. 6 c Spacing 23. 3 23. 2 Tenacity, g p d. 5. 8 5. 8 5.7 6.8 7. 6 8. 2 Elongation percent 13. 3 12. 4 11.8 13. 2 9. 4 9.0 Modulus, g.p.d 38 40 40 41 58 58 efliicency. The total draw ratio for the 6.4 gm./den.

yarn is thus 6X; X-ray examination shows that the yarn exhibits the HT crystal structure. The diffraction pattern shows the crystal to have a d spacing of 4.6 A., a c axis dimension of 24.1 A., and two spots at the 1st meridional reflection. The yarn has a T 13% greater 30 than the best yarn of Table 1. Since the calculated c axis dimension for this polymer is 26.8 A., the chains in this yarn are 90% fully extended.

EXAMPLE III PACM12 yarns of various tt. isomer content are drawn as shown in Table 4, with the properties and structure shown in the table. Drawing conditions are selected so that the HT crystal is produced in each case.

TABLE 4 A B C D E F Yarn properties:

Tenacity, g.p.d 3. 4 5. 2 6. 4 7.0 6. 3 6. 8 Elongation, percent.-." 11 12 1O 11 12 8 Modulus, g.p.d 35 40 46 51 44 71 d Spacing, A 4. 6 4. 6 4. 6 4. 6 4. 6 4. 6 c Spacing, A 23. 5 23. 4 24.1 23.8 23.8 24.0 Chain extension, percen 88 87 90 89 89 90 Angular separation, meridional eflect in (degrees). 3. 5 7. 4 11.0 10. 7 10. 0 12. 7

EXAMPLE II Polymer from PACM-l2 of 90% tt. isomer is melted and spun to yarn. The as-spun yarn has a relative viscosity of 141 and a birefringence of 0.0153. The yarn (1) is drawn 3.0 over a pin heated to C., then,

in a second draw stage, it is drawn 1.33 while in con- 50 tact with a series of three four-inch long plates heated to 160, and C., in succession. The total draw ratio is 4.0x; the feed roll speed is 4 ft./min. The X-ray diagram typical of this yarn shows substantially no lateral order (diffuse equatorial halo). When a hot plate is added, 55

(total yarn contact, about 32 inches) following the drawing step, to anneal the yarn at constant length at 230 C., yarn (2) having the A crystal is produced.

When an attempt is made to increase the (total) draw ratio to (3) 4.25 and (4) 4.5, the yarn tenacity at first increases, then decreases. The yarn (4) has transverse cracks, and many broken filaments are produced in draw- Elongation; percent- 1 Determined on annealed polymer flake.

8 .3 Modulus, g.p.d- 38 41 It is noted that in general, for the HT crystal that as the angular separation increases, the tenacity and initial modulus of the yarn increase.

EXAMPLE IV A series of yarns is spun from PACM polymerized with aliphatic dicarboxylic acids of 12, 14 or 16 carbon atoms and drawn under various conditions. Processing conditions, crystal form, d values (strong reflection) and c axis dimensions are listed in Table 5. The A crystal yarns are annealed at constant length to develop the crystal structure. This step is not required for the HT crystal yarns, although the percent crystallinity is increased by an annealing treatment, if it is carried out when the yarn is under drawing tension.

TABLE 5 7 EXAMPLE v Following a polymerization procedure similar to that shown in Example I, 90% tt. PACM-l2 polymer of 182.4 relative viscosity is prepared. The dried flake is fed to a screw melter spinning unit, and extruded to filaments at a spinneret temperature of 335 C. The yarn (RV 150) is drawn 3X over a snubbing pin heated to 155 C., then drawn while passed in a helical wrap around a pipe heated to 205 C. at the input end, 215 C. at the center, and 245 C. at the exit end. The overall draw ratio is 5.9x. This yarn is next drawn an additional 1.05 X using a snubbing pin heated to 160 C. followed by a plate heated to 240 C., as shown in the Hume patent. The yarn has a tenacity of 9.1 g.p.d. Both HT and EC crystal forms are present. The c axis dimension of the EC crystal is 26.5 A., which is about 98% of theoretical spacing. The d spacing is 4.4 A. The c spacing of the HT crystal is 23.8 A. and the d spacing is 4.6 A.

EXAMPLE VI Polymer of PACM-12 (PACM of 90% tt. isomer) is melted in a screw melter at a temperature of 330 C. and extruded through a filter pack and a 17 hole spinneret into an atmosphere of super-heated steam at 330 C. and then cooled in air. A lubricating finish is applied to the filaments which are then forwarded to a draw zone by means of a feed-separator roll combination at an input speed of 100 yd./ min. The yarn has a relative viscosity of 137.

The filaments pass around a 3-inch hot draw pin (150 C.) then around an intermediate pair of driven draw rolls and thence in two helical wraps around a pipe having sections heated to 210, 230, and 240 C., temperature increasing in the direction of yarn travel. The yarn next goes to a pair of annealing rolls heated to 240 C. There are 18 yarn wraps around these rolls. The filaments then go to a pair of forwarding rolls running at the same speed as the annealing rolls, and thence to a windup. Yarns at two different draw ratios are produced. Processing conditions, yarn properties and crystal structure are listed in Table 6.

EXAMPLE VII Copolymers are prepared and spun to a -fi1ament yarn using a screw melter, using the spinning and drawing conditions listed in Table 7. The yarn is not packaged between spinning and drawing. The yarn from Test 2 is subsequently stretched an additional 1.25 over a 1%" long hot plate at a temperature of 200 C., before testing h and X-ray analysis. Yarn properties and X-ray data are also given in the table. In the table, PACM- indicates the use of sebacic acid as the copolymer component. 6l2 indicates the use of hexamethylene diamine.

TABLE 7 Test 1 2 Major polymer component PACM-12 PACM-12 Minor component PA OM10 6-12 Ratio, by weight /30 70/30 Spinning temp., C 328 347 Superheatcd steam at spinneret, 328 347 Hot pin, temp. C 150 Pipe temp., 0.:

Zone 1 210 200 Zone 2.-. 223 215 Zone 3... 240 230 Draw rati0 4. 5X 2 4. 5X Yarn propert Denier 28. 8 22. 5

Relative viscosity 86 178 Tenacity, g.p.d 5. 9 5. 3

Elongation, percent- 9. 6 17. 1

Initial modulus, g.p 48 36 Crystal form HT HT (1 Spacing-.- 4.6 4. 5 c Spacing". 23. 4 23. 3

1 90 tt. 2 5.6Xtotal.

EXAMPLE VIII Following the procedure of Example V, high Viscosity 90 tt. PACM-l2 polymer is melted and extruded at 325 C. into a superheated steam atmosphere at 350 C. as a l40-filan1ent yarn. This yarn is drawn over a 3 diameter snubbing pin at C., by a pair of heated (160 C.) first-stage draw rolls to provide a 2.5x draw ratio. The yarn then passes in an S-wrap around two A" diameter draw pins heated to C., then-in 2 /2 helical wraps around a heated pipe at zoned temperatures of 210 C., 230 C. and 250 C. (exit end). The draw ratio in this stage is 1.-8 The hot yarn is cooled on the unheated second-stage draw rolls, from which it passes to the windup via tension let-down rolls. The yarn properties and X-ray structure are given in Table 8.

TABLE 8 Denier-840 Yarn relative viscosity300 Tenacity, g.p.d.-9.1 Elongation1 5 Initial modulus57 g.p.d. Crystal formHT and EC d Spacing, HT crystal4.5 A. d Spacing, EC crystal-4.3 A. c Axis, HT crystal23.2 A. 0 Axis, EC crystal-26.4 A.

PROCESSING VARIABLES As previously indicated, the filament crystal structure of this invention is obtained by heating the filaments to the specified temperature while under sufficient tension to induce permanent elongation or drawing. The filaments may be heated by using a hot plate, hot pin or pipe, molten metal or oil baths, or radiant heat. The essential feature is that the filament must attain the required temperature while under drawing tension. Drawing may be accomplished in one or more stages which may be combined as described in the Hume patent referred to previously. Alternatively, the drawing stages may be separated as for example by intermediate rolls so that the amount of drawing in each stage is mechanically controlled.

Oxidative degradation at melt temperatures should also be avoided. This is suitably accomplished by blanketing the spinneret with an inert gas, such as nitrogen or steam. It is especially desirable to use a heated inert gas since this provides an environment in which the molten filament can be reduced to the spinning or as-quenched denier with minimum orientation and maximum uniformity of cooling across the filament. This provides filaments which are more highly drawable than those produced with excessive spinning orientation.

Industrial yarn with the most desirable properties is usually attained by the use of PACM diamine of the highest tt. isomer content. Such properties are also enhanced by use of high molecular weight polymer, e.g., at least 15,000 mol. weight. Preferably, the molecular weight should be at least 18,000, and higher molecular weights are even more desirable. Practical considerations related to the high melt viscosity of the polymer suggest that polymer of 25,000 to 35,000 molecular weight be employed.

Within the general area of conditions that are suitable for producing the filament crystal structure of this invention, it is preferred that the filaments be exposed to the specified elevated temperatures while being subjected to an elongation of at least or greater. Even a very brief exposure of the filaments to the elevated temperatures has been found suitable for obtaining the desired crystal structure. Heating periods of from -50 milliseconds at the specified elevated temperature have yielded good results.

Application of processing conditions falling within the area described herein to filaments of high molecular weight polyamides consisting essentially of the following recurring structural units:

(A) H H I? O (H) wherein n is 10, 12 or 14 with at least 70% by weight of the diamino constituent of the repeating units being of a trans-trans stereoisomeric configuration has resulted in filaments having a transverse crystal spacing of 4.3 to 4.7 A. as determined from the strongest equatorial reflections in a Bragg X-ray diffraction pattern. The preferred filament polymer is that wherein n is 10. Depending upon the exact processing conditions employed, one is able to obtain filaments wherein the polymer chains are extended to at least 86% or even as much as 98% or greater of their theoretical fully extended length. The theoretical fully extended length is readily measured using Dreiding Stereomodels or Stuart and Brieglet models or may be calculated from standard bond lengths and angles by procedures well understood in the art. In this regard, reference may be made to International Tables For X-ray Crystallography, volume III, particularly page 276, Kynoch Press, Birmingham, England, (1962). Herein, fully extended c axis spacings have been calculated for PACM-14 and PACM-l6 as 29.3 and 31.8 A., respectively. For the purposes of this invention, the theoreti'cal fully extended length of a copolymer is assumed to be that of its major component.

COPOLYMERS In order to obtain fibers having maximum tenacity, dimensional stability, heat resistance and melting point, it is preferred to use homopolymer of PACM-l2, 14 or 16. However, for some uses, foreign or copolymer components may be added for example to increase dyeability, such as for seat-belt yarns, or to produce polymer having lower processing temperatures.

Some components have surprisingly little harmful effect on fiber.melting point, modulus or tenacity, hence may be used in larger amounts than one would normally expect would be acceptable.

Copolymer components, whether the foreign component replaces the amine, the acid or as an amino acid, replaces both, should be kept to no more than about by weight and preferably no more than about 15% if very high tenacities are desired. The percentage is calculated as the weight per 100 grams of polymer, of

or Z, where X referes to the acid entity in the foreign component, Y refers to the amine entity and Z refers to an amino acid component. These copolymer units may be added without serious loss in properties, or ability to form the HT crystal. For example, up to 30% of PACM- 10 9 to -16 may be used as copolymer components; these copolymer units appear to show a special compatibility in forming HT crystal with the major PACM12, 14 or 16 component.

Use of copolymer components which are structurally similar to PA CM (e.g., 4,4diaminodecyclohexylpropane- 2) also permits use of larger concentrations.

Replacement of both diacid and diamine with foreign components (as by copolymerizing with hexamethylene diamine and adipic acid) is not preferred since such practice introduces a wide variety of polymer repeat unit species into the crystal unit, tending to reduce HT-EC crystal content.

Suitable diamines for copolymerizing as Y- foreign components with (A) are diprimary or disecondary diamines, especially the alpha-omega aliphatic diamines of 2 and preferably 6 to 14 carbon atoms, such as hexamethylene diamine; 2-methylhexamethylene diamine; tetramethylhexamethylene diamine; 2,5-dimethyl hexamethylene diamine; di(aminopentyl)ether and di(aminopen tyl)sulfide. Ring-containing diamines include piperazine, substituted piperazines such as dimethyl piperazine; metaor para-xylylene diamine; 4,6-dimethylxylylenediamine; paraphenylene diamine, 4,6-dimethyl paraphenylene diamine; 4,4-diaminodicyclohexyl propane-2; 1,4-diaminomethylcyclohexane; 1,4-diamino-2,3-dimethyl cyclohexane; 1,4-cyclohexanediamine, and bis(2-sulfo-4-aminocyclohexyl)methane. Among suitable diacids for copolymerizing as PACMX components with (A) are alphaomega aliphatic acids of 2 to 16 carbon atoms; aromatic acids such as terephthalic acid, isophthalic acid, sulfonated isophthalic acid, para-phenylene diacetic acid, bibenzoic acid, 2-methyl terephthalic acid, and 1,4-cyclohexane dicarboxylic acid; 5,5-thiodivaleric acid; 5,5-oxydivaleric acid; di(4-carboxycyclohexyl)', bis (4-carboxycyclohexyl)methane; and bis(3methyl-4-carboxycyclohexyl)methane. Typical amino acids (or the corresponding lactams, when these exist) for copolymerizing as Z components with (A) include alpha, omega amino acids of from 2 to 12 carbon atoms between the nitrogen and carbonyl carbon; typical intermediates are pyrrolidone, 6-aminohexanoic acid, e-caprolactam, ll-aminoundecanoic acid and 12-aminododecanoic acid. Cyclic and/or aromatic amino acids may also be used, such as 4-piperidine carboxylic acid, m or p-aminobenzoic acid, 4- aminocyclohexaneacetic acid, and 4'-amino-4-bisphenyl carboxylic acid, 4-amino-4-carboxy(dicyclohexyl)methan ed; 4-aminocyclohexanoic acid; 3-aminocyclohexanoic ac1 It is apparent that copolymeric units which may be present are those which have divalent organic radicals containing from about 4 to about 20 carbon atoms, the divalent radical being joined into the linear polymer chain as an integral part thereof by amino and/or carbonyl radicals. By divalent organic radical is meant divalent radicals, bonded to the amino or carbonyl radicals through carbon, which radicals are predominantly hydrocarbon, but which (1) may be chain-interrupted by hetero atoms such as oxygen or sulfur, and/or (2) may have substituents for hydrogen which include radicals such as sulfonate, sulfate, phosphate, phosphinate, hydroxyl, acyl, and the like. Although it is preferred that a homopolyamide be used for the fiber of the present invention, copolymer components, when present, preferably consist of organic radicals which are hydrocarbon.

It should be noted that when copolymer components are present, lower drawing temperatures than those defined in Table I for the PACM 12, l4 or 16 component of the copolymer may usually be employed. As a guide, the drawing temperature is reduced the same number of degrees that the copolymer melting point is lowered below that of the corresponding PACM-l2, 14 or -16 homopolymer. Viscous flow drawing, however, should be avoided.

DIRECTIONS FOR USE The filaments of this invention are especially useful for tire cords. Processing conditions for 66 nylon are usually employed. For example, a 12 x 12 standard cord construction is used for 840 denier yarn, as with polyhexamethylene adipamide. The cord is dipped in resorcinolformaldehyde latex (RFL) adhesive and dried at 150 C. for 2 minutes at 2 lb. tension. The cord is then stretched 5 to 13% at 190 C. to 220 C. for 30 seconds to 1 minute. The tire is cured using conventional 66 nylon conditions.

UTILITY Fiber of this invention is especially useful in applications where high strength, high modulus and low shrinkage are desired. These include reinforcement of mechanical rubber goods, tires (particularly low flat spotting), belting, plastics, laminates, seat belts, tarpaulins, sail fabric, cordage, sewing thread and the like. The fiber can be used in form of continuous filament, monofil or multifil. Filaments of 1 to 50 denier are included as are heavier denier monofilaments, for example those of 5 to 50 mils diameter (0.12 to 1.25 mm.). The filaments may also be used as flock or staple. Other fibers may be combined therewith for reinforcement purposes.

What is claimed is:

1. A crystalline, oriented filament of a high molecular weight polymer consisting essentially of the following recurring structural units:

wherein n is 10, 12 or 14, at least 70% by weight of the diamino constituent of the repeating units being of a trans-trans stereoisomeric configuration, and said filament having a transverse crystal spacing of 4.3 to 4.7 A, as determined from the strongest equatorial reflections in a Bragg X-ray diffraction pattern and the polymer chains are extended to at least 86% of their theoretical fully extended length.

2. The filament of claim 1 wherein the polymer chains are extended to at least 98% of their theoretical fully extended length.

3. The filament of claim 1 wherein the angular separation of the meridional spots is at least about 4. The filament of claim 1 having a tenacity of at least 6 grams per denier.

5. A crystalline, oriented filament of a high molecular weight polymer wherein at least 70% by weight of the recurring structural units are of the formula:

H HO O being joined into the linear polymer chain as an integral part thereof by amino and/or carbonyl radicals, and said filament having a transverse crystal spacing of 4.3 to 4.7 A., as determined from the strongest equatorial reflections in a Bragg X-ray diffraction pattern, and wherein the polymer chains are extended to at least 86% of their theoretical length.

6. The filament of claim 5 wherein n is 10, having a tenacity of at least 6 grams per denier.

7. A crystalline, oriented filament of a high molecular weight polymer consisting essentially of at least 85% by weight of the recurring structural units of the formula:

where n is 10, 12 or 14 and with at least by weight of the diamino constituent of such repeating units being of a trans-trans stereoisomeric configuration, and said filament having a transverse crystal spacing of 4.3 to 4.7 A., as determined from the strongest equatorial reflections in a Bragg X-ray diffraction pattern, and wherein the polymer chains are extended to at least 86% of their theoretical length.

8. The filament of claim 7 wherein the polymer chains are extended to at least 98% of their theoretical length.

9. The filament of claim 7 wherein n is 10, having a tenacity of at least 6 grams per denier.

10. A crystalline, oriented filament of a high molecular weight polymer consisting essentially of the following recurring structural units:

at least 70% by weight of the diamino constituent of the repeating units being of a trans-trans stereoisomeric configuration, and said filament having a transverse crystal spacing of 4.3 to 4.7 A., as determined from the strong est equatorial reflections in a Bragg X-ray diffraction pattern, a c axis spacing of at least 23 A. and polymer chains which are extended to at least 86% of their theoretical fully extended length.

References Cited UNITED STATES PATENTS 2,512,606 6/ 1950 Bolton et a1. 26078 2,880,057 3/1959 Cuculo 26078 S 3,249,591 5/1966 Gadecki et a1. 3,091,015 5/1963 Zimmerman 28-72 3,393,210 7/1968 Speck 260-78 3,068,530 12/1962 Tin-Yam Au 264290 3,311,691 3/1967 Good 264-290 N 3,583,147 6/1971 Brizzolara et al. 26078 WILLIAM H. SHORT, Primary Examiner E. WOODBERRY, Assistant Examiner US. Cl. X.R.

57l40 R; 26078 S; 264-290 N 

